1. Field of the Invention
This invention relates to a magnetic recording tape cassette, and more particularly to a magnetic recording tape cassette having a guide member for guiding the magnetic tape and a tape pad pressed against the recording tape running along the guide member.
2. Description of the Prior Art
Recently, there have become available a video systems capable of ultra long video recording and reproduction, and VTRs (video tape recorders) which can memorize a recording schedule covering up to as long as a week and select TV programs to be recorded according to the memorized schedule. In such new video recording systems, six-hour recording is possible, while in conventional video recording systems only one- to two-hour recording is possible. Further, it is now expected that eight- to nine-hour recording will become possible in the near future.
In order to effect ultra long recording and reproduction of up to nine hours on tapes that can also be used with conventional recording and reproduction systems, it is necessary to enlarge the effective recording area of the magnetic recording tape. The effective recording area of a magnetic recording tape contained in a magnetic recording tape cassette can be enlarged by reducing the running speed of the recording tape, reducing the width of the recording track or increasing the actual surface area of the recording tape. However, the degree to which the running speed of the recording tape and the width of the recording track can be reduced is limited since the electromagnetic conversion efficiency must not be less than a certain value if the quality of the image and the sound is to be maintained at a satisfactory level. Thus it is necessary to increase the actual surface area of the magnetic recording tape contained in the cassette in order to lengthen the playing time of the video system. However the actual surface area of the magnetic recording tape contained in a cassette can be increased only by reducing the thickness of the magnetic recording tape to permit a longer magnetic recording tape to be contained in the cassette, since the diameter of the hub on which the tape is wound is standardized. Furthermore, high evenness of the surface of the magnetic recording tape is also required to improve the electromagnetic conversion efficiency.
However, when the thickness of the recording tape is reduced, the physical strength thereof is lowered and the tape is apt to be damaged by external forces. Further, high surface evenness of the tape generally results in backlash and other problems related to running instability and the high surface evenness is affected even by a small scratch on the surface of the tape, whereby stability of contact of the tape with the magnetic head is lost and the electromagnetic conversion characteristics are degraded.
As is well known, a tape pad is pressed against the rear surface of a magnetic recording tape when the tape is fed for recording or reproduction. This tape pad constitutes one of the elements imparting an external force which may damage the recording tape or cause the electromagnetic conversion characteristics to be degraded.